Schistosoma japonicum: semiquantitative assessment of circulating immune complexes, serum C1q and C3, and their relationship to renal pathology and hepatic fibrosis in rabbits

[Schistosoma-associated chronic septicemic salmonellosis: evolution of knowledge and immunopathogenic mechanisms]

Chronic septicemic salmonellosis is an individualized clinical entity characterized by prolonged fever with enlargement of the liver and spleen that occurs in Schistosoma-infected individuals who are coinfected with Salmonella. Several immunopathogenic mechanisms are involved, and they depend on the peculiarities of the interactions between Salmonella and various species of the genus Schistosoma. The modifications to the immune system that are caused by parasite infection are responsible for the evolution of the disease. In this review, we analyze the evolution of the knowledge on this entity and discuss the possible immuno-physiopathogenic mechanisms that contribute towards its development.

Hybridoma cell agglutination as a novel test to detect circulating antigen of Schistosoma japonicum

We developed a serodiagnostic test which is based on the agglutination of hybridoma cells. In the presence of specific antigen, agglutination of the fixed and stained cells occurs and can be visualized in analogy to traditional erythrocyte agglutination. The procedures were developed with a murine cell line producing a monoclonal antibody against a schistosome gut protein and sera of patients and mice infected with Schistosoma japonicum. This test is capable of detecting circulating antigen during pre-patency in mice infected with 50 cercariae. Its sensitivity was high with acute schistosomiasis japonica (97%, n = 32) and moderate with chronic cases (75%, n = 57). No positive reactions were obtained with healthy persons (n = 78) or patients infected with other parasites (Chlonorchis sinensis, n = 20; Paragonimus westermani, n = 20; Plasmodium vivax, n = 10) or suffering from lupus erythomatodus (n = 5) or mononucleosis (n = 10).

Schistosoma japonicum: the pathology of experimental infection

The pathology of experimental schistosomiasis japonica is reviewed and compared with the pathology of schistosomiasis japonica in man and to some aspects of schistosomiasis mansoni and schistosomiasis haematobia in experimental animals. The induction of granulomas around Schistosoma japonicum eggs depends upon cell mediated immunity, as do the reactions to Schistosoma mansoni and Schistosoma haematobium eggs. However, the modulation of the reaction to S. japonicum eggs can be greatly influenced by antibody, while antibody has no effect on the granulomas around S. mansoni eggs. Adult worm pairs of S. japonicum tend to cluster in the mesenteric venules, and most eggs are laid in a few sites. This leads to large, focal intestinal lesions similar to the discrete lesions produced by S. haematobium in the intestine and urinary tract but in contrast to the widespread, diffuse lesions produced by S. mansoni. Comparison with S. japonicum infection in humans is limited chiefly by our scant knowledge of the pathology produced by S. japonicum in infected persons. Most such comparisons are, in any case, limited by the marked differences in the reactions of various experimental host species to the infection and by differences in the reaction of a given host species to different strains of the parasite.

Schistosoma japonicum: immunological response to circulating polysaccharide antigens in rabbits with a light infection

To study the detectability of circulating polysaccharide antigens and the immunological response to such antigens in rabbits with a light Schistosoma japonicum infection, sera of five rabbits infected with 50 cercariae were studied up to 29 weeks post infection (p.i.). While one rabbit developed no worm burden, the other rabbits developed low worm burdens (4 to 16 worms). In the sera of these rabbits, the only polysaccharide antigen demonstrable with immunoelectrophoresis (IEF), was the circulating anodic antigen (CAA). With the enzyme-linked immunosorbent assay (ELISA), CAA was detectable from 5 to 6 weeks p.i. in the sera of the two rabbits with the highest number of worm couples. The lowest CAA level which was detectable in unconcentrated sera from which serum proteins had been removed was 125 ng CAA/ml, corresponding with a worm burden of 4.5 worm/kg body wt. During the entire infection, CAA-specific immune complexes were only demonstrable in very low concentrations. Antibodies against polysaccharide antigens were assessed with immunofluorescent antibody (IFA) on Rossman's fixed sections of adult worms, with the ELISA, and with IEF. Specific IgA, IgG, and IgM antibodies were detectable from 2 to 3 weeks p.i. with IFA and ELISA. These early antibodies were shown to be directed against gut-associated antigens, while antibodies against parenchyma-associated antigens were found later in the infection. With IEF, antibodies against two trichloroacetic acid (TCA)-soluble antigens were detectable, including the major, S. japonicum-specific antigen 2.

Immunoglobulin M-Immunoglobulin G mixed cryoglobulinemia in Schistosoma japonicum-infected rabbits

Cryoprecipitation was observed in defibrinated serum from Schistosoma japonicum-infected rabbits. Ouchterlony immunodiffusion, sodium dodecyl sulfate-polyacrylamide gels, and anti-cryoprecipitate antiserum demonstrated the presence of immunoglobulin G (IgG), IgM, C3, fibrinogen, and an alpha-macroglobulin. Parasite antigen was not detected. IgG and IgM from pooled cryoprecipitates failed to react with each other in Ouchterlony immunodiffusion gels after separation by column chromatography. The data suggest that the IgG and IgM are not specifically complexed with each other but may simply be aggregates of altered proteins.

Immune complex glomerulonephritis and amyloidosis in Schistosoma japonicum infected rabbits

Epidemiologically, the incidence of renal pathology in patients with chronic parasitic infections is higher than expected. In particular, schistosomiasis may have an association with renal failure. 24 New Zealand White rabbits were, therefore infected with 250 or 500 Schistosoma japonicum cercariae of the Philippine-Leyte strain and studied for eight months to determine if rabbits with long-term infections were suitable hosts for the study of schistosomal nephropathy. Clinical evidence for renal disease consisted of proteinuria, haematuria, and casts. Of the 18 surviving infected animals, six had trace amounts of protein in their urine, three had significant proteinuria ranging from 100 to 300 mg%, four exhibited haematuria and 14 were positive for the presence of proteinaceous cast formation. The clinical findings correlated with the histological data. Periodic open renal biopsies on a subgroup of the animals revealed no changes until about the sixth month. At eight months after infection, five (28%) of the 18 rabbits had amyloid deposits and 15 (83%) had some degree of renal change which included mild focal, diffuse intracapillary, and crescentic glomerulonephritis with mesangial and subendothelial complex trapping. Periodic-acid Schiff staining graphically demonstrated wire loops and tubular casts. Immunofluorescence showed that 15 (83%) of the infected animals exhibited diffuse mesangial and peripheral capillary wall deposition of IgG while 14 contained IgM (78%). The third component of complement was found in only five (28%) of the infected rabbits. Parasite antigen could not be detected in the glomeruli of any of the animals. Kidneys from age-matched controls were within normal limits. Electron microscopy of glomeruli from several animals demonstrated the presence of subendothelial and mesangial immune complex deposition similar to that seen in systemic lupus erythematosus. These findings show that schistosomiasis japonica in the rabbit offers an excellent model system for studying not only the renal pathology associated with human schistosomiasis but also the pathogenesis of amyloidosis which is a frequent sequela observed in a variety of chronic inflammatory infections.

Experimental renal disease due to schistosomiasis

Although there is a marked variability in the development of renal lesions among individual animal models of schistosomal infections, much has been learned about the mechanisms leading to renal injury. The lesions in S. mansoni and S. japonicum infections correspond quite closely to the immune complex type of lesions, with complement involvement. The main antigens involved seem to be polysacharides of worm-gut origin, but participation of other antigens (including soluble egg antigens) cannot be excluded. Many observations testify to the localization of immune complexes, preformed in circulation, but the possibility that antigens, filtered through glomeruli, deposit incapillary walls first and bind with corresponding antibodies later on should be considered also. Deoxyribonucleic acids also may play a role in the pathogenesis. The perpetuation of the lesions is probably due to constant supply of antigens. In some models, renal pathology was related to the dose of infection, but in others there was no relation to worm burden. Renal pathology in S. haematobium infections is different, being related to the lower urinary tract, with obstructive lesions causing pyelonephritis and hydronephrosis.